Stacked chip-on-board module with edge connector

ABSTRACT

A module can include a module card and first and second microelectronic elements having front surfaces facing a first surface of the module card. The module card can also have a second surface and a plurality of parallel exposed edge contacts adjacent an edge of at least one of the first and second surfaces for mating with corresponding contacts of a socket when the module is inserted in the socket. Each microelectronic element can be electrically connected to the module card. The front surface of the second microelectronic element can partially overlie a rear surface of the first microelectronic element and can be attached thereto.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser. No. 13/306,203, filed Nov. 29, 2011, which claims the benefit of the filing date of U.S. Provisional Patent Application Ser. No. 61/477,820, filed Apr. 21, 2011, the disclosures of which are hereby incorporated by reference herein. The following commonly-owned applications are hereby incorporated by reference herein: U.S. Provisional Patent Application Ser. Nos. 61/477,877, 61/477,883, and 61/477,967, all filed Apr. 21, 2011.

BACKGROUND OF THE INVENTION

The present invention relates to stacked microelectronic assemblies and methods of making such assemblies, and to components useful in such assemblies.

Semiconductor chips are commonly provided as individual, prepackaged units. A standard chip has a flat, rectangular body with a large front face having contacts connected to the internal circuitry of the chip. Each individual chip typically is mounted in a package which, in turn, is mounted on a circuit panel such as a printed circuit board and which connects the contacts of the chip to conductors of the circuit panel. In many conventional designs, the chip package occupies an area of the circuit panel considerably larger than the area of the chip itself.

As used in this disclosure with reference to a flat chip having a front face, the “area of the chip” should be understood as referring to the area of the front face. In “flip chip” designs, the front face of the chip confronts the face of a package substrate, i.e., the chip carrier, and the contacts on the chip are bonded directly to contacts of the chip carrier by solder balls or other connecting elements. In turn, the chip carrier can be bonded to a circuit panel through terminals overlying the front face of the chip. The “flip chip” design provides a relatively compact arrangement; each chip occupies an area of the circuit panel equal to or slightly larger than the area of the chip's front face, such as disclosed, for example, in certain embodiments of commonly-assigned U.S. Pat. Nos. 5,148,265; 5,148,266; and 5,679,977, the disclosures of which are incorporated herein by reference.

Certain innovative mounting techniques offer compactness approaching or equal to that of conventional flip-chip bonding. Packages which can accommodate a single chip in an area of the circuit panel equal to or slightly larger than the area of the chip itself are commonly referred to as “chip-sized packages.”

Besides minimizing the planar area of the circuit panel occupied by microelectronic assembly, it is also desirable to produce a chip package that presents a low overall height or dimension perpendicular to the plane of the circuit panel. Such thin microelectronic packages allow for placement of a circuit panel having the packages mounted therein in close proximity to neighboring structures, thus reducing the overall size of the product incorporating the circuit panel.

Various proposals have been advanced for providing plural chips in a single package or module. In the conventional “multi-chip module,” the chips are mounted side-by-side on a single package substrate, which in turn can be mounted to the circuit panel. This approach offers only limited reduction in the aggregate area of the circuit panel occupied by the chips. The aggregate area is still greater than the total surface area of the individual chips in the module.

It has also been proposed to package plural chips in a “stack” arrangement, i.e., an arrangement where plural chips are placed one on top of another. In a stacked arrangement, several chips can be mounted in an area of the circuit panel that is less than the total area of the chips. Certain stacked chip arrangements are disclosed, for example, in certain embodiments of the aforementioned U.S. Pat. Nos. 5,679,977; 5,148,265; and U.S. Pat. No. 5,347,159, the disclosure of which is incorporated herein by reference. U.S. Pat. No. 4,941,033, also incorporated herein by reference, discloses an arrangement in which chips are stacked on top of another and interconnected with one another by conductors on so-called “wiring films” associated with the chips.

Despite the advances that have been made in multi-chip packages, there is still a need for improvements in order to minimize the size and improve the performance of such packages. These attributes of the present invention are achieved by the construction of the microelectronic assemblies as described hereinafter.

BRIEF SUMMARY OF THE INVENTION

In accordance with an aspect of the invention, a module can include a module card and first and second microelectronic elements having front surfaces facing a first surface of the module card. The module card can also have a second surface and a plurality of parallel exposed edge contacts adjacent an edge of at least one of the first and second surfaces for mating with corresponding contacts of a socket when the module is inserted in the socket. Each microelectronic element can be electrically connected to the module card. The front surface of the second microelectronic element can partially overlie a rear surface of the first microelectronic element and can be attached thereto.

In a particular embodiment, the second microelectronic element can have a plurality of chip contacts exposed at the front surface thereof projecting beyond a lateral edge of the first microelectronic element. In one embodiment, the edge contacts can be exposed at at least one of the first or second surfaces of the module card. In an exemplary embodiment, at least some of the edge contacts can be exposed at the second surface. In a particular embodiment, the module can also include an encapsulant covering the first and second microelectronic elements and a portion of the module card. In one embodiment, the encapsulant can be an overmold. In an exemplary embodiment, at least one of the first and second microelectronic elements can include a memory storage element. In a particular embodiment, at least one of the first and second microelectronic elements can include a DRAM element.

In one embodiment, the module can also include a plurality of leads extending from chip contacts of the at least one of the first and second microelectronic elements to the edge contacts. The leads can be usable to carry an address signal usable to address the memory storage element in at least one of the first and second microelectronic elements. In a particular embodiment, at least some of the edge contacts can be usable to carry at least one of a signal or a reference potential between the respective edge contact and each of the first and second microelectronic elements. In an exemplary embodiment, the module card can consist essentially of a material having a coefficient of thermal expansion of less than 30 ppm/° C.

In an exemplary embodiment, the module can also include a spacer extending between the front surface of the second microelectronic element and the first surface of the module card. The spacer can have substantially the same thickness in a vertical direction substantially perpendicular to the first surface as the first microelectronic element. In one embodiment, the module can also include a compliant die attachment adhesive bonding the front surface of the first microelectronic element to the first surface of the module card. In a particular embodiment, the first microelectronic element can be flip-chip bonded to the module card. In an exemplary embodiment, the second microelectronic element can be flip-chip bonded to the module card.

In a particular embodiment, the module card can also include an aperture extending between the first and second surfaces. The module can also include a plurality of leads extending within the aperture from chip contacts of at least one of the first and second microelectronic elements to the edge contacts. In one embodiment, the aperture can be aligned with the chip contacts of the at least one of the first and second microelectronic elements. In an exemplary embodiment, the aperture can be aligned with the chip contacts of the first and second microelectronic elements. In a particular embodiment, the leads can extend along the first surface. In one embodiment, the leads can extend along the second surface.

In one embodiment, the aperture can have a long dimension extending in a direction away from an edge of the module card. In an exemplary embodiment, the aperture can be a first aperture, and the module card can also include a second aperture extending between the first and second surfaces. Each of the first and second apertures can be aligned with the chip contacts of the respective first and second microelectronic elements. In a particular embodiment, the module can also include an encapsulant covering portions of the leads between the chip contacts and the module card. In one embodiment, the leads can include conductive elements on the module card and wire bonds extending from the conductive elements to the chip contacts of the at least one of the first and second microelectronic elements.

In an exemplary embodiment, the leads can include conductive elements on the module card and lead bonds extending from the conductive elements to the chip contacts of the at least one of the first and second microelectronic elements. In a particular embodiment, the plurality of leads can extend from chip contacts of the first microelectronic element to the edge contacts. In one embodiment, the plurality of leads can extend from chip contacts of the second microelectronic element to the edge contacts.

In a particular embodiment, the module can also include a plurality of third microelectronic elements. Each third microelectronic element can be electrically connected to the module card. In an exemplary embodiment, the plurality of third microelectronic elements can be arranged in a stacked configuration. Each of the third microelectronic elements can have a front or rear surface confronting a front or rear surface of an adjacent one of the third microelectronic elements. In one embodiment, the plurality of third microelectronic elements can be arranged in a planar configuration. Each of the third microelectronic elements can have a peripheral surface confronting a peripheral surface of an adjacent one of the third microelectronic elements. In a particular embodiment, the second microelectronic element can include volatile RAM, the third microelectronic elements can each include nonvolatile flash memory, and the first microelectronic element can include a processor configured to predominantly control transfers of data between an external component and the second and third microelectronic elements. In an exemplary embodiment, the second microelectronic element can include a volatile frame buffer memory storage element, the third microelectronic elements can each include nonvolatile flash memory, and the first microelectronic element can include a graphics processor.

In accordance with another aspect of the invention, a module can include a module card, first and second microelectronic elements, and a plurality of leads. The module card can have a first surface, a second surface, and a plurality of parallel exposed edge contacts adjacent an edge of at least one of the first and second surfaces for mating with corresponding contacts of a socket when the module is inserted in the socket. The first microelectronic element can have a rear surface facing the first surface of the module card. The second microelectronic element can have a front surface facing the first surface of the module card. Each microelectronic element can be electrically connected to the module card. The second microelectronic element can partially overlie a front surface of the first microelectronic element and can be attached thereto. The plurality of leads can extend from chip contacts of the second microelectronic element to the edge contacts.

In a particular embodiment, the module card can further include an aperture extending between the first and second surfaces. The plurality of leads can extend within the aperture. In one embodiment, the second microelectronic element can be flip-chip bonded to the module card. In an exemplary embodiment, a component can include first and second modules as described above bonded to one another. The second surfaces of the module cards can face one another.

In accordance with yet another aspect of the invention, a module can include a lead frame, first and second microelectronic elements having front surfaces facing a first surface of the lead frame, and an encapsulant covering the first and second microelectronic elements and a portion of the lead frame. The lead frame can also have a second surface and a plurality of exposed module contacts adjacent an edge of at least one of the first and second surfaces for mating with corresponding contacts of a socket when the module is inserted in the socket. Each microelectronic element can be electrically connected to the lead frame. The front surface of the second microelectronic element can partially overlie a rear surface of the first microelectronic element and can be attached thereto.

In one embodiment, a component can include first and second modules as described above bonded to one another. The second surfaces of the lead frames can face one another. In an exemplary embodiment, a system can include a plurality of modules as described above, a circuit panel, and a processor. The exposed contacts of the modules can be inserted into a mating socket electrically connected with the circuit panel. Each module can be configured to transfer a number N of data bits in parallel in a clock cycle. The processor can be configured to transfer a number M of data bits in parallel in a clock cycle. M can be greater than or equal to N.

Further aspects of the invention can provide systems that incorporate modules and/or components according to the foregoing aspects of the invention, composite chips according to the foregoing aspects of the invention, or both in conjunction with other electronic components electrically connected thereto. For example, the system can be disposed in and/or mounted to a single housing, which can be a portable housing. Systems according to preferred embodiments in this aspect of the invention can be more compact than comparable conventional systems.

In accordance with still another aspect of the invention, a method of fabricating a module can include providing a module card, mounting first and second microelectronic elements onto the module card, and electrically connecting the first and second microelectronic elements to the module card. The module card can have a first surface, a second surface, and a plurality of exposed edge contacts adjacent an edge of at least one of the first and second surfaces for mating with corresponding contacts of a socket when the module is inserted in the socket. Front surfaces of the first and second microelectronic elements can face the first surface of the module card. The front surface of the second microelectronic element can partially overlie a rear surface of the first microelectronic element and can be attached thereto.

In an exemplary embodiment, the module card can further include an aperture extending between the first and second surfaces. The module can also include a plurality of leads extending within the aperture from chip contacts of at least one of the first and second microelectronic elements to the edge contacts. In a particular embodiment, the leads can include conductive elements on the module card. The step of electrically connecting the first and second microelectronic elements to the module card can electrically connect the conductive elements to the chip contacts of at least one of the first and second microelectronic elements using a bonding tool inserted through the aperture.

In one embodiment, the leads can include wire bonds extending from the conductive elements to the chip contacts. In an exemplary embodiment, the leads can include lead bonds extending from the conductive elements to the chip contacts. In a particular embodiment, the method can also include the step of injecting an encapsulant onto the rear surfaces of the microelectronic elements and the first surface of the module card. In one embodiment, the encapsulant can be a first encapsulant. The method can also include the step of injecting a second encapsulant into the aperture such that portions of the leads between the chip contacts and the module card are covered by the second encapsulant.

In a particular embodiment, the step of mounting first and second microelectronic elements onto the module card can include applying a compliant die attachment adhesive between the first surface of the module card and the front surface of the first microelectronic element. In an exemplary embodiment, the method can also include the step of mounting a spacer between the front surface of the second microelectronic element and the first surface of the module card. The spacer can have substantially the same thickness in a vertical direction substantially perpendicular to the first surface as the first microelectronic element.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagrammatic sectional view of a stacked microelectronic assembly according to an embodiment of the present invention.

FIG. 1B is a bottom sectional view of the stacked assembly of FIG. 1A, taken along the line 1B-1B of FIG. 1A.

FIG. 1C is a side sectional view of the stacked assembly of FIG. 1B, taken along the line 1C-1C of FIG. 1B.

FIG. 2 is a diagrammatic sectional view of a stacked microelectronic assembly according to another embodiment having a flip-chip bonded microelectronic element.

FIG. 3 is a diagrammatic sectional view of a stacked microelectronic assembly according to another embodiment having a face-up microelectronic element.

FIG. 4 is a diagrammatic sectional view of a stacked microelectronic assembly according to another embodiment having a single window in the module card through which wire bonds attached to two microelectronic elements extend.

FIG. 5 is a diagrammatic sectional view of a stacked microelectronic assembly according to another embodiment having lead bonds.

FIG. 6 is a diagrammatic sectional view of a stacked microelectronic assembly according to another embodiment having elongated solder connects.

FIG. 7 is a diagrammatic sectional view of a stacked microelectronic assembly according to another embodiment having a microelectronic element with contacts located near an edge thereof.

FIG. 8 is a variation of the bottom sectional view of the stacked assembly of FIG. 1B, in which one microelectronic elements has rows of central contacts oriented substantially perpendicular to rows of central contacts of another microelectronic element.

FIG. 9A is a diagrammatic sectional view of a stacked microelectronic assembly according to another embodiment having a lead frame.

FIG. 9B is a bottom sectional view of the stacked assembly of FIG. 9A, taken along the line 9B-9B of FIG. 9A.

FIG. 9C is a side sectional view of the stacked assembly of FIG. 9B, taken along the line 9C-9C of FIG. 9B.

FIG. 10A is a diagrammatic top view of a stacked microelectronic assembly according to another embodiment having a plurality of stacked microelectronic elements, shown without an encapsulant.

FIG. 10B is a side sectional view of the stacked assembly of FIG. 10A, taken along the line 10B-10B of FIG. 10A.

FIG. 10C is a diagrammatic top view of a stacked microelectronic assembly according to another embodiment having a plurality of microelectronic elements adjacent to one another.

FIG. 11 is a diagrammatic perspective view of a stacked microelectronic assembly according to another embodiment including two module cards bonded to one another.

FIG. 12 is a schematic depiction of a system according to one embodiment including a plurality of modules.

FIG. 13 is a top plan view of a microelectronic element in the embodiment of FIG. 1A.

FIG. 14 is a top plan view of another microelectronic element in the embodiment of FIG. 1A.

DETAILED DESCRIPTION

With reference to FIGS. 1A through 1C, a module 10 according to an embodiment of the present invention can include a first microelectronic element 20, a second microelectronic element 30, and a module card 40 having exposed edge contacts 50. A first encapsulant 60 can cover the microelectronic elements 20 and 30 and a portion of the module card 40.

In some embodiments, at least one of the first and second microelectronic elements 20 and 30 can be a semiconductor chip, a wafer, or the like. For example, one or both of the first microelectronic element 20 and the second microelectronic element 30 can include a memory storage element such as a DRAM. As used herein, a “memory storage element” refers to a multiplicity of memory cells arranged in an array, together with circuitry usable to store and retrieve data therefrom, such as for transport of the data over an electrical interface. In a particular example, the module 10 can be included in a single in-line memory module (“SIMM”) or a dual in-line memory module (“DIMM”).

The first microelectronic element 20 can have a front surface 21, a rear surface 22 remote therefrom, and lateral edges 23 extending between the front and rear surfaces. Electrical contacts 24 are exposed at the front surface 21 of the first microelectronic element 20. As described herein, the electrical contacts 24 of the first microelectronic element 20 can also be referred to as “chip contacts.” As used in this disclosure, a statement that an electrically conductive element is “exposed at” a surface of a structure indicates that the electrically conductive element is available for contact with a theoretical point moving in a direction perpendicular to the surface toward the surface from outside the structure. Thus, a terminal or other conductive element which is exposed at a surface of a structure can project from such surface; can be flush with such surface; or can be recessed relative to such surface and exposed through a hole or depression in the structure. The contacts 24 of the first microelectronic element 20 are exposed at the front surface 21 within a central region 25 of the first microelectronic element. For example, the contacts 24 can be arranged in one or two parallel rows adjacent the center of the front surface 21.

The second microelectronic element 30 can have a front surface 31, a rear surface 32 remote therefrom, and lateral edges 33 extending between the front and rear surfaces. Electrical contacts 34 are exposed at the front surface 31 of the second microelectronic element 30. As described herein, the electrical contacts 34 of the second microelectronic element 30 can also be referred to as “chip contacts.” The contacts 34 of the second microelectronic element 30 are exposed at the front surface 31 within a central region 35 of the second microelectronic element. For example, the contacts 34 can be arranged in one or two parallel rows adjacent the center of the front surface 31.

As seen in FIGS. 1A and 1C, the first and second microelectronic elements 20 and 30 can be stacked relative to one another. In some embodiments, the front surface 31 of the second microelectronic element 30 and the rear surface 22 of the first microelectronic element 20 can face one another. At least a portion of the front surface 31 of the second microelectronic element 30 can overlie at least a portion of the rear surface 22 of the first microelectronic element 20. At least a portion of the central region 35 of the second microelectronic element 30 can project beyond a lateral edge 23 of the first microelectronic element 20. Accordingly, the contacts 34 of the second microelectronic element 30 can be positioned in a location projecting beyond the lateral edge 23 of the first microelectronic element 20.

The microelectronic assembly 10 can further include a module card 40 having oppositely-facing first and second surfaces 41 and 42. One or more electrically conductive contacts 44 can be exposed at the second surface 42 of the module card 40. The module card 40 can further include one or more apertures such as the first aperture 45 and the second aperture 46. As shown in FIGS. 1A and 1C, the front surfaces 21, 31 of the respective first and second microelectronic elements 20, 30 can face the first surface 41 of the module card 40.

The module card 40 can be partly or entirely made of any suitable dielectric material. For example, the module card 40 may comprise a relatively rigid, board-like material such as a thick layer of fiber-reinforced epoxy, such as Fr-4 or Fr-5 board. Regardless of the material employed, the module card 40 may include a single layer or multiple layers of dielectric material. In a particular embodiment, the module card 40 can consist essentially of a material having a coefficient of thermal expansion (“CTE”) of less than 30 ppm/° C.

As seen in FIG. 1, the module card 40 may extend beyond a lateral edge 23 of the first microelectronic element 20 and a lateral edge 33 of the second microelectronic element 30. The first surface 41 of the module card 40 may be juxtaposed with the front surface 21 of the first microelectronic element 20.

In the embodiment depicted in FIGS. 1A through 1C, the module card 40 includes a first aperture 45 substantially aligned with the central region 25 of the first microelectronic element 20 and a second aperture 46 substantially aligned with the central region 35 of the second microelectronic element 30, thereby providing access to contacts 24 and 34 through the respective first and second apertures. The first and second apertures 45 and 46 can extend between the first and second surfaces 41 and 42 of the module card 40. As shown in FIG. 1B, the apertures 45 and 46 can be aligned with the corresponding chip contacts 24 or 34 of the respective first and second microelectronic elements 20 and 30.

The module card 40 may also include electrically conductive contacts 44 exposed at the second surface 42 thereof and electrically conductive traces 55 extending between the contacts 44 and the exposed edge contacts 50. The electrically conductive traces 55 electrically couple the contacts 44 to the exposed edge contacts 50. In a particular embodiment, the contacts 44 can be end portions of respective ones of the traces 55.

In a particular embodiment, the module card 40 can have a plurality of parallel exposed edge contacts 50 adjacent an insertion edge 43 of at least one of the first and second surfaces 41, 42 for mating with corresponding contacts of a socket (shown in FIG. 12) when the module 10 is inserted in the socket. As shown in FIG. 1B, the insertion edge 43 can be located such that each of the apertures 45 and 46 have a long dimension L extending in a direction away from the insertion edge of the module card 40. Some or all of the edge contacts 50 can be exposed at either or both of the first or second surfaces 41, 42 of the module card 40.

The exposed edge contacts 50 and the insertion edge can be sized for insertion into a corresponding socket (FIG. 12) of other connector of a system, such as can be provided on a motherboard. Such exposed edge contacts 50 can be suitable for mating with a plurality of corresponding spring contacts (FIG. 12) within such socket connector. Such spring contacts can be disposed on single or multiple sides of each slot to mate with corresponding ones of the exposed edge contacts 50. In one example, at least some of the edge contacts 50 can be usable to carry at least one of a signal or a reference potential between the respective edge contact and each of the first and second microelectronic elements 20, 30.

As seen in FIGS. 1A through 1C, electrical connections or leads 70 can electrically connect the contacts 24 of the first microelectronic element 20 and the contacts 34 of the second microelectronic element 30 to the exposed edge contacts 50. The leads 70 may include wire bonds 71 and 72 and the conductive traces 55. In one embodiment, the leads 70 can be considered to electrically connect each microelectronic element 20, 30 to the module card 40. In a particular example, the leads 70 can be usable to carry an address signal usable to address a memory storage element in at least one of the first and second microelectronic elements 20, 30.

As used herein, a “lead” is a portion of or the entire electrical connection extending between two electrically conductive elements, such as the lead 70 comprising wire bonds 71 and a conductive trace 55 that extends from one of the contacts 24 of the first microelectronic element 20, through the first aperture 45, to one of the exposed edge contacts 50.

In one example, the module 10 can include a plurality of leads 70 extending within the apertures 45 and 46 from chip contacts 24 and 34 of at least one of the first and second microelectronic elements 20 and 30 to the exposed edge contacts 50. In a particular embodiment, the leads 70 can include the conductive traces 55 on the module card 40 and the wire bonds 71, 72 extending from the conductive traces to the chip contacts 24, 34 of at least one of the first and second microelectronic elements 20, 30.

As shown in FIG. 1B, the conductive traces 55 of the leads 70 can extend along the second surface 42 of the module card 40. In a particular example, the conductive traces 55 of the leads 70 can extend along the first surface 41 of the module card 40, or the conductive traces of the leads can extend along both the first and second surfaces 41, 42 of the module card. Portions of the conductive traces 55 can extend along a surface 41 or 42 of the module card 40 in a direction approximately parallel to the long dimensions L of the apertures 45 and 46 from the respective contacts 24 and 34 to the exposed edge contacts 50. In a particular embodiment, the conductive traces 55 be arranged in a pattern along a surface 41 or 42 of the module card 40 such that the length of the leads 70 between the respective contacts 24 and 34 and the exposed edge contacts 50 can be minimized.

Each of the wire bonds 71 and 72 can extend through the respective first or second aperture 45 or 46 and can electrically couple a contact respective 24 or 34 to a corresponding contact 44 of the module card 40. The process of forming the wire bonds 71 and 72 can include inserting a bonding tool through the apertures 45, 46 to electrically connect the conductive contacts 24, 34 to corresponding conductive contacts 44 of the module card 40.

In a particular embodiment, each of the wire bonds 71 and 72 can be a multiple wire bond including a plurality of wire bonds oriented substantially parallel to one another. Such a multiple wire bond structure including a plurality of wire bonds 71 or 72 can provide electrically parallel conductive paths between a contact 24 or 34 and a corresponding contact 44 of the module card 40.

A spacer 12 can be positioned between the front surface 31 of the second microelectronic element 30 and a portion of the first surface 41 of the module card 40. Such a spacer 12 can be made, for example, from a dielectric material such as silicon dioxide, a semiconductor material such as silicon, or one or more layers of adhesive. If the spacer 12 includes adhesives, the adhesives can connect the second microelectronic element 30 to the module card 40. In one embodiment, the spacer 12 can have substantially the same thickness T1 in a vertical direction V substantially perpendicular to the first surface 41 of the module card 40 as the thickness T2 of the first microelectronic element 20 between the front and rear surfaces 21, 22 thereof.

In a particular embodiment, the spacer 12 can be replaced by a buffering chip having a surface facing the first surface 41 of the module card 40. In one example, such a buffering chip can be flip-chip bonded to contacts exposed at the first surface 41 of the module card 40. Such a buffering chip can be configured to help provide impedance isolation for each of the microelectronic elements 20 and 30 with respect to components external to the module 10.

One or more adhesive layers 14 can be positioned between the first microelectronic element 20 and the module card 40, between the first and second microelectronic elements 20 and 30, between the second microelectronic element 30 and the spacer 12, and between the spacer 12 and the module card 40. Such adhesive layers 14 can include adhesive for bonding the aforementioned components of the module 10 to one another. In a particular embodiment, the one or more adhesive layers 14 can extend between the first surface 41 of the module card 40 and the front surface 21 of the first microelectronic element 20. In one embodiment, the one or more adhesive layers 14 can attach at least a portion of the front surface of the second microelectronic element 30 to at least a portion of the rear surface 22 of the first microelectronic element 20.

In one example, each adhesive layer 14 can be partly or entirely made of a die attachment adhesive and can be comprised of a low elastic modulus material such as silicone elastomer. In one embodiment, the die attachment adhesive can be compliant. In another example, each adhesive layer 14 can be entirely or partly made of a thin layer of high elastic modulus adhesive or solder if the two microelectronic elements 20 and 30 are conventional semiconductor chips formed of the same material, because the microelectronic elements will tend to expand and contract in unison in response to temperature changes. Regardless of the materials employed, each of the adhesive layers 14 can include a single layer or multiple layers therein. In a particular embodiment where the spacer 12 is made from an adhesive, the adhesive layers 14 positioned between the spacer 12 and the second microelectronic element 30 and the module card 40 can be omitted.

The module 10 can also include a first encapsulant 60 and a second encapsulant 65. The first encapsulant 60 can cover, for example, the rear surfaces 22 and 32 of the respective first and second microelectronic elements 20 and 30 and a portion of the first surface 41 of the module card 40. In a particular embodiment, the first encapsulant 60 can be an overmold. One or more second encapsulants 65 can cover portions of the front surfaces 21 and 31 of the respective microelectronic elements 20 and 30 exposed within the respective apertures 45 and 46, a portion of the second surface 42 of the module card 40, the contacts 24, 34, and 44, and the wire bonds 71 and 72 extending between the respective contacts 24 and 34 and the corresponding contacts 44. In a particular embodiment, a second encapsulant 65 can cover portions of the leads 70 extending between the chip contacts 24 and 34 and the module card 40.

In a process according to a particular embodiment, the first encapsulant 60 can be injected onto the rear surfaces 22 and 32 of the respective first and second microelectronic elements 20 and 30 and onto the first surface of the module card 40. In a process according to one example, the second encapsulant 65 can be injected into the first and second apertures 45, 46 such that portions of the leads 70 between the chip contacts 24, 34 and the module card 40 are covered by the second encapsulant.

FIG. 2 shows a variation of the embodiment described above with respect to FIGS. 1A through 1C. In this variation, a module 210 is the same as the module 10 described above, except that the first microelectronic element 220 is flip-chip bonded to the first surface 241 of the module card 240, rather than being wire-bonded to the second surface of the module card.

Conductive contacts 224 are exposed at the front surface 221 of the first microelectronic element 220. The conductive contacts or chip contacts 224 can be electrically connected to conductive contacts 247 exposed at the first surface 241 of the module card 240, for example, by conductive masses 273. The conductive masses 273 can comprise a fusible metal having a relatively low melting temperature, e.g., solder, tin, or a eutectic mixture including a plurality of metals. Alternatively, the conductive masses 273 can include a wettable metal, e.g., copper or other noble metal or non-noble metal having a melting temperature higher than that of solder or another fusible metal. In a particular embodiment, the conductive masses 273 can include a conductive material interspersed in a medium, e.g., a conductive paste, e.g., metal-filled paste, solder-filled paste or isotropic conductive adhesive or anisotropic conductive adhesive.

Conductive traces (not shown in FIG. 2) can extend from the conductive contacts 247 along the first surface 241 of the module card 240 to exposed edge contacts at an insertion edge of the module card such as the insertion edge 43 shown in FIGS. 1B and 1C. As in the module 10 described above, chip contacts 234 of the second microelectronic element 230 can be electrically connected to corresponding conductive contacts 244 of the module card 240 by wire bonds 272 extending through an aperture 246 of the module card. Conductive traces can also extend from the conductive contacts 244 along the second surface 242 of the module card 240 to exposed edge contacts at an insertion edge of the module card such as the insertion edge 43 shown in FIGS. 1B and 1C.

FIG. 3 shows another variation of the embodiment described above with respect to FIGS. 1A through 1C. In this variation, a module 310 is the same as the module 10 described above, except that the first microelectronic element 320 is positioned with the rear surface 322 thereof facing the first surface 341 of the module card 340 and at least a portion of the front surface 321 thereof facing and partially overlying at least a portion of the front surface 331 of the second microelectronic element 330. The rear surface 322 of the first microelectronic element 320 can be attached to the first surface 341 of the module card 340 by one or more adhesive layers such as the adhesive layers 14 shown in FIGS. 1A and 1C. Conductive contacts 324 a and 324 b (collectively conductive contacts 324) can be exposed at the front surface 321 of the first microelectronic element 320. The chip contacts 324 of the first microelectronic element 320 can include any configuration of conductive contacts 324 a and/or 324 b.

The conductive contacts 324 a of the first microelectronic element 320 can be exposed at the front surface 321 within a central region 325 of the first microelectronic element. For example, the contacts 324 a can be arranged in one or two parallel rows adjacent the center of the front surface 321. The conductive contacts 324 a can be electrically connected to conductive contacts 347 exposed at the first surface 341 of the module card 340, for example, by wire bonds 371 a.

The conductive contacts 324 b of the first microelectronic element 320 can be exposed at the front surface 321 near a lateral edge 323 of the first microelectronic element. For example, the contacts 324 b can be arranged in one or two parallel rows adjacent the lateral edge 323 of the first microelectronic element 320. The conductive contacts 324 b can be electrically connected to conductive contacts 347 exposed at the first surface 341 of the module card 340, for example, by wire bonds 371 b.

Similar to FIG. 2, conductive traces (not shown in FIG. 3) can extend from the conductive contacts 347 and 344 along the respective first and second surfaces 341, 342 of the module card 340 to exposed edge contacts at insertion edges of the module card such as the insertion edge 43 shown in FIGS. 1B and 1C.

Although the embodiment shown in FIG. 3 is shown with the second microelectronic element 330 being electrically connected to the module card 340 by wire bonds 372, in other embodiments, the second microelectronic element can be electrically connected to the module card in various other ways, including for example, lead bonds (as shown in FIG. 5) or flip-chip bonding with solder (as shown in FIGS. 6 and 7).

FIG. 4 shows another variation of the embodiment described above with respect to FIGS. 1A through 1C. In this variation, a module 410 is the same as the module 10 described above, except that first and second microelectronic elements 410 and 420 are electrically connected to the module card 440 by respective wire bonds 471 and 472 extending through a common aperture 446 extending between first and second surfaces 441, 442 of the module card, rather than having each microelectronic element be electrically connected to the module card by wire bonds extending through respective separate apertures of the module card.

As shown in FIG. 4, the conductive contacts 424 of the first microelectronic element 420 can be exposed at the front surface 421 near a lateral edge 423 of the first microelectronic element. For example, the contacts 424 can be arranged in a row adjacent the lateral edge 423 of the first microelectronic element 420. The conductive contacts 424 can be electrically connected to conductive contacts 444 exposed at the second surface 442 of the module card 440, for example, by wire bonds 471.

The conductive contacts 434 of the second microelectronic element 430 can be exposed at the front surface 431 within a central region 435 of the second microelectronic element. For example, the contacts 434 can be arranged in a row approximately at the center of the front surface 431. The conductive contacts 434 can be electrically connected to conductive contacts 444 exposed at the second surface 442 of the module card 440, for example, by wire bonds 472.

In the embodiment shown in FIG. 4, the module 410 can include a single second encapsulant 465. For example, a second encapsulant 65 can cover portions of the front surfaces 421 and 431 of the respective microelectronic elements 420 and 430 exposed within the single common aperture 446, a portion of the second surface 442 of the module card 440, the contacts 424, 434, and 444, and the wire bonds 471 and 472 extending between the respective contacts 424 and 434 and the corresponding contacts 444.

FIG. 5 shows another variation of the embodiment described above with respect to FIGS. 1A through 1C. In this variation, a module 510 is the same as the module 10 described above, except that the first microelectronic element 520 is flip-chip bonded to the first surface 541 of the module card 540 (in the same manner as in FIG. 2), and the second microelectronic element 530 is electrically connected to the module card 540 by lead bonds 574 a and 574 b (collectively the lead bonds 574) extending from conductive traces to the chip contacts 534 rather than by wire bonds.

As shown in FIG. 5, the conductive contacts 534 a and 534 b (collectively the conductive contacts 534) of the second microelectronic element 530 can be exposed at the front surface 531 within a central region 535 of the second microelectronic element. For example, the contacts 534 can be arranged in one or two parallel rows adjacent the center of the front surface 531. Some of the conductive contacts 534 a can be electrically connected to conductive contacts 544 exposed at the second surface 542 of the module card 540, for example, by lead bonds 574 a. Others of the conductive contacts 534 b can be electrically connected to conductive contacts 547 exposed at the first surface 541 of the module card 540, for example, by lead bonds 574 b. As shown in FIG. 5, the conductive contacts 544 and 547 can be conductive contact portions of the respective lead bonds 574 a and 574 b.

The process of forming the lead bonds 574 can generally be as described in commonly assigned U.S. Pat. Nos. 5,915,752 and 5,489,749, the disclosures of which are incorporated by reference herein. In the lead bonding process, each lead 570 can be displaced downwardly by a tool such as a thermosonic bonding tool into engagement with a corresponding conductive contact 534. Such a bonding tool can be inserted through the aperture 546 to electrically connect the leads 570 to the corresponding conductive contacts 534. Frangible sections of the leads 570 can be broken during this process.

FIG. 6 shows another variation of the embodiment described above with respect to FIGS. 1A through 1C. In this variation, a module 610 is the same as the module 10 described above, except that the first microelectronic element 620 is flip-chip bonded to the first surface 641 of the module card 640 (in the same manner as in FIG. 2), and the second microelectronic element 630 is flip-chip bonded to the first surface of the module card by conductive masses 675 extending between the conductive contacts 634 of the second microelectronic element and conductive contacts 647 exposed at the first surface of the module card rather than by wire bonds. In a particular embodiment, the module card 640 can be devoid of leads extending through apertures between the first and second surfaces 641, 642 thereof, such as the apertures 45 and 46 shown in FIG. 1A.

Similar to the module 10 described above, the conductive contacts 634 of the second microelectronic element 630 can be exposed at the front surface 631 within a central region 635 of the second microelectronic element. For example, the contacts 634 can be arranged in one or two parallel rows adjacent the center of the front surface 631.

The conductive masses 675 can be, for example, elongated solder connects, solder balls, or any other material described above with reference to the conductive masses 273. Such conductive masses 675 can extend through the space between the spacer 612 and the lateral edge 623 of the first microelectronic element 620 to electrically connect the second microelectronic element 630 with the module card 640.

FIG. 7 shows another variation of the embodiment described above with respect to FIG. 6. In this variation, a module 710 is the same as the module 610 described above, except that the second microelectronic element 730 is flip-chip bonded to the first surface 741 of the module card 740 by conductive masses 775 extending between conductive contacts 734 located adjacent a lateral edge 733 of the second microelectronic element and conductive contacts 747 exposed at the first surface of the module card, rather than having the conductive masses extend between conductive contacts exposed at the front surface of the second microelectronic element within a central region of the second microelectronic element.

In a particular example, the contacts 734 can be arranged in a row adjacent the lateral edge 733 of the second microelectronic element 730, such that the contacts 734 can project beyond the lateral edge 723 of the first microelectronic element 720. In one embodiment, similar to the module 610 described above, the module card 740 can be devoid of leads extending through apertures between the first and second surfaces 741, 742 thereof.

FIG. 8 shows another variation of the embodiment described above with respect to FIG. 1B. In this variation, a module 810 is the same as the module 10 described above, except that the rows of conductive contacts 824 of the first conductive element 820 can be substantially perpendicular to the rows of conductive contacts 834 of the second conductive element 830. In such an embodiment, the second aperture 846 can have a long dimension L extending in a direction away from the insertion edge 843 of the module card 840, similar to the second aperture 46 shown in FIG. 1B. The first aperture 845 can be have a long dimension L′ extending in a direction substantially parallel to the insertion edge 843 of the module card 840 and substantially perpendicular to the long dimension L of the second aperture 846.

The leads 870 can include a pattern of conductive traces 855 a that is the same as the pattern of conductive traces 55 shown in FIG. 1B. The leads 870 can further include an alternate pattern of conductive traces 855 b extending from the conductive contacts 844 b exposed at the second surface 842 of the module card 840 to the exposed edge contacts 850. In a particular embodiment, some of the conductive traces 855 b can extend around lateral edges 848 of the first aperture 845.

FIG. 9 shows a variation of the embodiment described above with respect to FIGS. 1A through 1C. In this variation, a module 910 is the same as the module 10 described above, except that the first and second microelectronic elements 920 and 930 are mounted onto a lead frame 980 rather than being mounted onto a module card such as the module card 40 shown in FIG. 1A. In a particular embodiment, the front surfaces 921, 931 of the first and second microelectronic elements 920, 930 can face a first surface 981 of the lead frame 980, each microelectronic element being electrically connected to the lead frame.

Examples of lead frame structures are shown and described in U.S. Pat. Nos. 7,176,506 and 6,765,287, the disclosures of which are hereby incorporated by reference herein. In general, a lead frame such as the lead frame 980 is a structure formed from a sheet of conductive metal, such as copper, that is patterned into segments including a plurality of leads or conductive trace portions 985. In example embodiments, at least one of the first and second microelectronic element 920, 930 can be mounted directly onto the leads, which can extend under the microelectronic elements. In such an embodiment, contacts 924, 934 on the microelectronic elements can be electrically connected to respective leads by solder balls or the like. The leads can then be used to form electrical connections to various other conductive structures for carrying an electronic signal potential to and from the microelectronic elements 920, 930. When the assembly of the structure is complete, which can include forming an encapsulation layer 960 thereover, temporary elements such as a frame (not shown) can be removed from the leads of the lead frame 980, so as to form individual leads or conductive trace portions 985.

The first microelectronic element 920 can be attached to the lead frame 980 by one or more adhesive layers 914 extending between the front surface 921 of the first microelectronic element and a first surface 981 of the lead frame. Such adhesive layers 914 can be similar to the adhesive layers 14 described above with reference to FIGS. 1A through 1C. The spacer 912 can be attached to the lead frame 980 be one or more adhesive layers 914 extending between a front surface 913 of the spacer and the first surface 981 of the lead frame. At least a portion of the front surface 931 of the second microelectronic element 930 can partially overlie the rear surface 922 of the first microelectronic element 920 and a rear surface 915 of the spacer 912. The front surface 931 of the second microelectronic element 930 can be attached to the rear surface 922 of the first microelectronic element 920 and the rear surface 915 of the spacer 912 by one or more adhesive layers 914.

As seen in FIGS. 9A through 9C, electrical connections or leads 970 can electrically connect the contacts 924 of the first microelectronic element 920 and the contacts 934 of the second microelectronic element 930 to the exposed module contacts 950. The leads 970 may include wire bonds 971 and 972 and conductive trace portions 985 of the lead frame 980. In a particular example, the leads 970 can be usable to carry an address signal usable to address a memory storage element in at least one of the first and second microelectronic elements 920, 930.

In one example, the lead frame 980 can define a first gap 945 and a second gap 946 extending between the first surface 981 of the lead frame and a second surface 982 of the lead frame opposite the first surface. The first gap 945 can be aligned with the chip contacts 924 of the first microelectronic element 920, such that the wire bonds 971 can extend between the chip contacts 924 and the second surface 982 of the lead frame through the first gap. The second gap 946 can be aligned with the chip contacts 934 of the second microelectronic element 930, such that the wire bonds 972 can extend between the chip contacts 934 and the second surface 982 of the lead frame through the second gap.

The module 910 can also include an encapsulant 960 that can cover the first and second microelectronic elements 20, 30 and a portion of the lead frame 980, such that the exposed module contacts 950 can be exposed at a lower surface 962 of an insertion portion 961 of the encapsulant. The encapsulant 960 can also cover the contacts 924, 934, and the wire bonds 971 and 972 extending between the respective contacts 924 and 934 and the lead frame 980. The insertion portion 961 of the encapsulant 960 can have an appropriate size and shape for mating with a corresponding socket (shown in FIG. 12) when the module 910 is inserted in the socket.

In a particular embodiment, the module 910 can have a plurality of parallel exposed module contacts 950 adjacent an insertion edge 983 of at least one of the first and second surfaces 981, 982 for mating with corresponding contacts of a socket (shown in FIG. 12) when the module 910 is inserted in the socket. Some or all of the module contacts 950 can be exposed at either or both of the first or second surfaces 981, 982 of the lead frame 980.

FIGS. 10A and 10B show a variation of the embodiment described above with respect to FIG. 2. In this variation, a module 1010 is the same as the module 210 described above, except that the module 1010 also includes a stack of third microelectronic elements 1090 mounted onto the module card 1040.

Similar to FIG. 2, the first microelectronic element 1020 is flip-chip bonded to the first surface 1041 of the module card 1040. The conductive contacts or chip contacts 1024 of the first microelectronic element 1020 can be electrically connected to conductive contacts 1047 exposed at the first surface 1041 of the module card 1040, for example, by conductive masses 1073. Chip contacts 1034 of the second microelectronic element 1030 can be electrically connected to corresponding conductive contacts 1044 of the module card 1040 by wire bonds 1072 extending through an aperture 1046 of the module card. Conductive traces (not shown in FIGS. 10A and 10B) can extend from the conductive contacts 1044 and 1047 along the first surface 1041 and/or the second surface 1042 of the module card 1040 to exposed edge contacts 1050 at an insertion edge of the module card such as the edge 1043 or the edge 1043 a. As shown in FIG. 10B, the edge contacts 1050 can be exposed at the first surface 1041, the second surface 1042, or both surfaces.

There can be any number of third microelectronic elements 1090 in the stack, including, for example, two third microelectronic elements 1090 a and 1090 b as shown in FIG. 10B. The third microelectronic elements 1090 can be connected with one another and/or with the edge contacts 1050 by any interconnection configuration. For example, the lower third microelectronic element 1090 a can be connected with contacts exposed at a surface of the module card 1040 via flip-chip bonding, wire bonds, lead bonds, or other interconnection configurations. One or more upper third microelectronic elements 1090 b can be connected with contacts of the module card 1040 through conductive vias extending through the lower third microelectronic element 1090 a, wire bonds, lead bonds, or other interconnection configurations.

In an exemplary embodiment, the module 1010 can be configured to function as a solid state memory drive. In such an example, the first microelectronic element 1020 can include a semiconductor chip configured predominantly to perform a logic function, such as a solid state drive controller, and the second microelectronic element 1030 can include a memory storage element such as volatile RAM, for example, DRAM. The third microelectronic elements 1090 can each include memory storage elements such as nonvolatile flash memory. The first microelectronic element 1020 can include a special purpose processor that is configured to relieve a central processing unit of a system such as the system 1200 (FIG. 12) from supervision of transfers of data to and from the memory storage elements included in the second microelectronic element 1030 and the third microelectronic elements 1090. Such a first microelectronic element 1020 including a solid state drive controller can provide direct memory access to and from a data bus on a motherboard (e.g., the circuit panel 1202 shown in FIG. 12) of a system such as the system 1200.

In another embodiment, the module 1010 can be configured to function as a graphics module, for example, that can be plugged into a PCI express slot of a notebook personal computer. In such an example, the first microelectronic element 1020 can include a semiconductor chip configured predominantly to perform a logic function, such as a graphics processor, and the second microelectronic element 1030 can include a memory storage element such as volatile RAM (e.g., DRAM) that can serve as a volatile frame buffer for computational graphics rendering. The third microelectronic elements 1090 can each include memory storage elements such as nonvolatile flash memory.

FIG. 10C shows a variation of the embodiment described above with respect to FIGS. 10A and 10B. In this variation, a module 1010′ is the same as the module 1010 described above, except that the module 1010′ includes a plurality of third microelectronic elements 1090′ mounted onto the module card 1040 adjacent to one another rather than in a stacked configuration. Similar to the module 1010, the third microelectronic elements 1090′ can be connected with contacts exposed at a surface of the module card 1040 by any interconnection configuration, such as flip-chip bonding, wire bonds, lead bonds, or other interconnection configurations. The module 1010′ can be used for similar exemplary functions as the module 1010, such as a solid state memory drive or a graphics module.

FIG. 11 depicts a component 1100 including first and second modules 1110 a and 1110 b according to any of the embodiments described above, such as for example, the module 10 described with reference to FIGS. 1A through 1C. The first and second modules 1110 a, 1110 b can be bonded to one another with at least one layer 1165, such that the second surfaces 1142 of the respective module cards 1140 of the modules can face one another. In a particular embodiment, the at least one layer 1165 can be a single common encapsulant such as the second encapsulant 65 shown in FIGS. 1A and 1B. In another example, the at least one layer 1165 can be one or more adhesive layers, similar to the adhesive layers 14 described with reference to FIGS. 1A through 1C.

The component 1100 can have one or more rows of parallel exposed edge contacts 1150 adjacent an insertion edge 1143 of the component. Each of the first and second modules 1110 a, 1110 b can have a row of edge contacts 1150 exposed at the first surface 1141 of the respective module card 1140, such that the edge contacts can be suitable for mating with corresponding contacts of a socket (similar to the socket shown in FIG. 12) when the component 1100 is inserted in the socket.

The modules and components described above with reference to FIGS. 1A through 10 can be utilized in construction of diverse electronic systems, such as the system 1200 shown in FIG. 12. For example, the system 1200 in accordance with a further embodiment of the invention includes a plurality of modules or components 1206 as described above in conjunction with other electronic components 1208 and 1210.

The system 1200 can includes a plurality of sockets 1205, each socket including a plurality of contacts 1207 at one or both sides of the socket, such that each socket 1205 can be suitable for mating with corresponding exposed edge contacts or exposed module contacts of a corresponding module or component 1206. In the exemplary system 1200 shown, the system can include a circuit panel or motherboard 1202 such as a flexible printed circuit board, and the circuit panel can include numerous conductors 1204, of which only one is depicted in FIG. 12, interconnecting the modules or components 1206 with one another. However, this is merely exemplary; any suitable structure for making electrical connections between the modules or components 1206 can be used.

In a particular embodiment, the system 1200 can also include a processor such as the semiconductor chip 1208, such that each module or component 1206 can be configured to transfer a number N of data bits in parallel in a clock cycle, and the processor can be configured to transfer a number M of data bits in parallel in a clock cycle, M being greater than or equal to N.

In one example, the system 1200 can include a processor chip 1208 that is configured to transfer thirty-two data bits in parallel in a clock cycle, and the system can also include four modules 1206 such as the module 10 described with reference to FIGS. 1A through 1C, each module 1206 configured to transfer eight data bits in parallel in a clock cycle (i.e., each module 1206 can include first and second microelectronic elements, each of the two microelectronic elements being configured to transfer four data bits in parallel in a clock cycle).

In another example, the system 1200 can include a processor chip 1208 that is configured to transfer sixty-four data bits in parallel in a clock cycle, and the system can also include four modules 1206 such as the component 1000 described with reference to FIG. 12, each module 1206 configured to transfer sixteen data bits in parallel in a clock cycle (i.e., each module 1206 can include two sets of first and second microelectronic elements, each of the four microelectronic elements being configured to transfer four data bits in parallel in a clock cycle).

In the example depicted in FIG. 12, the component 1208 is a semiconductor chip and component 1210 is a display screen, but any other components can be used in the system 1200. Of course, although only two additional components 1208 and 1210 are depicted in FIG. 12 for clarity of illustration, the system 1200 can include any number of such components.

Modules or components 1206 and components 1208 and 1210 can be mounted in a common housing 1201, schematically depicted in broken lines, and can be electrically interconnected with one another as necessary to form the desired circuit. The housing 1201 is depicted as a portable housing of the type usable, for example, in a cellular telephone or personal digital assistant, and screen 1210 can be exposed at the surface of the housing. In embodiments where a structure 1206 includes a light-sensitive element such as an imaging chip, a lens 1211 or other optical device also can be provided for routing light to the structure. Again, the simplified system shown in FIG. 12 is merely exemplary; other systems, including systems commonly regarded as fixed structures, such as desktop computers, routers and the like can be made using the structures discussed above.

Turning to FIG. 13, the first microelectronic element 136 may be any type of semiconductor chip. In this embodiment, the first microelectronic element 136 can be a DRAM (dynamic random access memory) chip having conductive elements thereon. As shown, the surface area of the front surface 140 of the first microelectronic element 136 may be divided into three regions having substantially equal widths in a direction between the first and second edges of the first microelectronic element: a first outer region 1320, a second outer region 1322, and a central region 1324 positioned between the first outer region 1320 and second outer region 1322. For example, if the length between the long edges is 6 microns, the respective lengths of the first outer, second outer, and central regions may be 2 microns. The central region 1324 would therefore be positioned 2 microns from the first edge 144 and 2 microns from the second edge 144. In other words, the central region can be positioned in the middle third of the first microelectronic element 136.

As is typical with regard to DRAM chips, the conductive elements may include first bond pads 142 that extend along the central region 1324 of the front surface 140 of the first microelectronic element 136. The conductive elements provide for an electrical connection between the first microelectronic element 136 and the first set of contacts 109 positioned on the second surface 106 of the substrate 102. An adhesive 101 can be used to attach the first microelectronic element 136 to the substrate 102.

The second microelectronic element 153 may be similar to the first microelectronic element 136. A front surface 157 of the second microelectronic element having bond pads thereon, faces the first microelectronic element 136, such that the second microelectronic element 153 overlies the rear surface 138 of the first microelectronic element 136. As shown in FIG. 14, in this embodiment, the second microelectronic element 153 has opposed first and second edges 161, 162 and opposed third and fourth edges 163, 164 extending between the rear surface 155 and front surface 157 of the second microelectronic element 153 and adjacent first and second edges 161, 162. Conductive elements, such as bond pads 159, extend along the front surface 157 of the second microelectronic element 153. In this embodiment, the second microelectronic element 153 may be a semiconductor chip, such as a DRAM chip, with bond pads 159 positioned along a central region 1332 of the second microelectronic element 153, which is positioned between a first outer region 1328 and a second outer region 1330. In one embodiment, bond pads 159 can extend in a direction transverse to the direction bond pads 142 on the first microelectronic element 136 extend.

A possible benefit of a module or component according to the invention, for example the module 10 described above with reference to FIGS. 1A through 1C, whereby a surface of the first microelectronic element overlies at least a portion of the rear surface of the second microelectronic element can be to provide relatively short leads electrically connecting a particular exposed edge contact (e.g., the exposed edge contact 50) a particular electrical contact (e.g., the electrical contact 24) exposed at a front surface of a particular microelectronic element (e.g., the first microelectronic element 20). Parasitic capacitance can be considerable between adjacent leads, particularly in microelectronic assemblies that have high contact density and fine pitch. In microelectronic assemblies such as the module 10 where the leads 70 can be relatively short, parasitic capacitance can be reduced, particularly between adjacent leads.

Another possible benefit of a module or component according to the invention as described above can be to provide similar lengths of leads such as the leads 70, for example, which can electrically connect data input/output signal terminals (e.g., the exposed edge contacts 50) with electrical contacts 24, 34 at the front surfaces of respective first and second microelectronic elements 20, 30. In systems such as the system 1200 that can include a plurality of modules or components 1206, having relatively similar-length leads 70 can allow the propagation delay for data input/output signals between each microelectronic element and the exposed edge contacts to be relatively closely matched.

Yet another possible benefit of a module or component according to the invention as described above can be to provide similar lengths of leads such as the leads 70, for example, which can electrically connect shared clock signal terminals and/or shared data strobe signal terminals (e.g., the exposed edge contacts 50) with electrical contacts 24, 34 at the front surfaces of respective first and second microelectronic elements 20, 30. The data strobe signal terminals or the clock signal terminals or both may have substantially the same loading and electrical path lengths to the respective microelectronic elements 20, 30 and the path lengths to each microelectronic element can be relatively short.

In any or all of the modules or components described in the foregoing, the rear surface of one or more of the first or second microelectronic elements can be at least partially exposed at an exterior surface of the microelectronic assembly after completing fabrication. Thus, in the assembly described above with respect to FIGS. 1A through 1C, one or both of the rear surfaces 22, 32 of the first and second microelectronic elements 20, 30 can be partially or fully exposed in the completed module 10. The rear surfaces 22, 32 can be partially or fully exposed although an overmold such as the first encapsulant 60, or other encapsulating or packaging structures can contact or be disposed adjacent the microelectronic elements.

In any of the embodiments described above, the microelectronic assembly may include a heat spreader made of metal, graphite or any other suitable thermally conductive material. In one embodiment, the heat spreader includes a metallic layer disposed adjacent to the first microelectronic element. The metallic layer may be exposed on the rear surface of the first microelectronic element. Alternatively, the heat spreader can include an overmold or an encapsulant covering at least the rear surface of the first microelectronic element.

Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.

It will be appreciated that the various dependent claims and the features set forth therein can be combined in different ways than presented in the initial claims. It will also be appreciated that the features described in connection with individual embodiments may be shared with others of the described embodiments. 

1. A module, comprising: a module card having a first surface, a second surface, and a plurality of parallel exposed edge contacts adjacent an edge of at least one of the first and second surfaces for mating with corresponding contacts of a socket when the module is inserted in the socket; first and second microelectronic elements, the first microelectronic element having a rear surface facing the first surface of the module card, the second microelectronic element having a front surface facing the first surface of the module card, each microelectronic element being electrically connected to the module card, the second microelectronic element partially overlying a front surface of the first microelectronic element and attached thereto; and a plurality of leads extending from chip contacts of the second microelectronic element to the edge contacts.
 2. A module as claimed in claim 1, wherein the module card further includes an aperture extending between the first and second surfaces, the plurality of leads extending within the aperture.
 3. A module as claimed in claim 1, wherein the second microelectronic element is flip-chip bonded to the module card.
 4. A module, comprising: a lead frame having a first surface, a second surface, and a plurality of exposed module contacts adjacent an edge of at least one of the first and second surfaces for mating with corresponding contacts of a socket when the module is inserted in the socket; first and second microelectronic elements having front surfaces facing the first surface of the lead frame, each microelectronic element being electrically connected to the lead frame, the front surface of the second microelectronic element partially overlying a rear surface of the first microelectronic element and attached thereto; and an encapsulant covering the first and second microelectronic elements and a portion of the lead frame.
 5. A component including first and second modules according to claim 4 bonded to one another, wherein the second surfaces of the lead frames face one another.
 6. A method of fabricating a module, comprising: providing a module card having a first surface, a second surface, and a plurality of exposed edge contacts adjacent an edge of at least one of the first and second surfaces for mating with corresponding contacts of a socket when the module is inserted in the socket; mounting first and second microelectronic elements onto the module card, such that front surfaces of the first and second microelectronic elements face the first surface of the module card, and such that the front surface of the second microelectronic element partially overlies a rear surface of the first microelectronic element and is attached thereto; and electrically connecting the first and second microelectronic elements to the module card.
 7. A method as claimed in claim 6, wherein the module card further includes an aperture extending between the first and second surfaces, the module further comprising a plurality of leads extending within the aperture from chip contacts of at least one of the first and second microelectronic elements to the edge contacts.
 8. A method as claimed in claim 7, wherein the leads include conductive elements on the module card, and the step of electrically connecting the first and second microelectronic elements to the module card electrically connects the conductive elements to the chip contacts of at least one of the first and second microelectronic elements using a bonding tool inserted through the aperture.
 9. A method as claimed in claim 8, wherein the leads include wire bonds extending from the conductive elements to the chip contacts.
 10. A method as claimed in claim 8, wherein the leads include lead bonds extending from the conductive elements to the chip contacts. 